Design of Coarse-Fine CSI Feedback for Beamforming in Next-Generation WLANs

This paper proposes a feedback technique to improve beamforming within multiple-input multiple-output (MIMO) systems using correlated multi-antenna channels. The method distinguishes between ‘coarse CSI’, which is derived from channel statistics, and ‘fine CSI’, which is obtained through a single channel sounding. The primary direction of the beam is determined using coarse CSI, which is then combined with fine CSI to capture the channel’s instantaneous characteristics, with effective feedback being provided through codebook-based feedback and Givens rotations. Additionally, an unequal modulation method is employed across different signal-to-noise ratio (SNR) intervals to refine the dynamic range of the SNR and determine the optimal modulation and coding scheme (MCS) for each interval, facilitating SNR adaptation. Simulation results demonstrate that the proposed scheme significantly enhances throughput and reduces packet error rates in comparison to existing wireless local area network (WLAN) schemes.